U.S. Pat. No. 6,034,096 reports the preparation of (A) while U.S. Pat. No. 7,329,689 indicates the characteristics and the preparation of a monohydrate polymorph form of the compound (A), called polymorph form I.
U.S. Pat. No. 6,034,096, example 12, actually reports the preparation of compound (A) wherein the product is isolated as a white solid having a melting point of 162-165° C. (with decomposition). In U.S. Pat. No. 7,329,689, with reference to U.S. Pat. No. 6,034,096, it is stated that the product obtained according to U.S. Pat. No. 6,034,096 is an anhydrous, amorphous, hygroscopic and deliquescent product, difficult to handle. A novel monohydrate crystalline form of the compound (A), particularly advantageous for industrial use in that it is stable and easier to handle with respect to the anhydrous product described previously, is actually described in U.S. Pat. No. 7,329,689.